Because collagen is inherently piezoelectric, research is being actively conducted to utilize it to harvest energy. In this study, a collagen solution was prepared using edible low-molecular-weight peptide collagen powder, and collagen films were fabricated using a dip coating method. The collagen films prepared by dip coating showed a smooth surface without defects such as pinholes or cracks. Dehydrothermal treatment of the collagen films was performed to induce a stable molecular structure through cross-linking. The collagen film subjected to dehydrothermal treatment at 110 °C for 24 h showed a thickness reduction rate of 19 %. Analysis of the collagen films showed that the crystallinity of the collagen film improved by about 7.9 % after dehydrothermal treatment. A collagen film-based piezoelectric nanogenerator showed output characteristics of approximately 13.7 V and 1.4 μA in a pressure test of 120 N. The generator showed a maximum power density of about 2.91 mW/m2 and an output voltage of about 8~19 V during various human body movements such as finger tapping. The collagen film-based piezoelectric generator showed improved output performance with improved crystallinity and piezoelectricity after dehydrothermal treatment.

BaTiO3-Poly vinylidene fluoride (PVDF) solution was prepared by adding 0~25 wt% BaTiO3 nanopowder and 10 wt% PVDF powder in solvent. BaTiO3-PVDF film was fabricated by spreading the solution on a glass with a doctor blade. The output performance increased with increasing BaTiO3 concentration. When the BaTiO3 concentration was 20 wt%, the output voltage and current were 4.98 V and 1.03 μA at an applied force of 100 N. However, they decreased when the over 20 wt% BaTiO3 powder was added, due to the aggregation of particles. To enhance the output performance, the generator was poled with an electric field of 150~250 kV/cm at 100 °C for 12 h. The output performance increased with increasing electric field. The output voltage and current were 7.87 V and 2.5 μA when poled with a 200 kV/cm electric field. This result seems likely to be caused by the c-axis alignment of the BaTiO3 after poling treatment. XRD patterns of the poled BaTiO3-PVDF films showed that the intensity of the (002) peak increased under high electric field. However, when the generator was poled with 250 kV/cm, the output performance of the generator degraded due to breakdown of the BaTiO3-PVDF film. When the generator was matched with 800 Ω resistance, the power density of the generator reached 1.74 mW/m2. The generator was able to charge a 10 μF capacitor up to 1.11 V and turn on 10 red LEDs.